Thanks, Lazur! It sounds like that's where the problem lies. If I ungroup the two lines in the "wrong" option, then group them again, the line width is indeed correct. I think this solves the issue; thanks once more!

Thanks for your reply! The settings are Optimized, with all the check boxes checked. I tried different settings, but no difference thus far...

I'm drawing a three-line shape where all lines have stroke width 0.5mm, as indicated in the Stroke style tab. However, in reality some of the lines turn out to be slightly fatter than the others, even if the values in the tab are the same. After some experimenting I found out that this is caused by ...